Blocks all other parts of the spectrum in the UV and IR. The Astronomik UV-IR Blocker is the ideal choice as a luminance filter for any kind of digital photography. Because of the perfect blocking of UV and IR, all optical problems in these parts of the spectrum are avoided. It blocks the heat from reaching your filter and diagonal as well. The filter is optimized for systems with focal ratios between f/0.5 and f/50. The typical transmission is higher than 99%.